This invention relates to machines for making tubing of multiple layers of material and more particularly to machines for making wood tubing from layers of thin wood veneer.
A variety of machines for making tubes of multiple layers of wood material have been proposed but none have been particularly effective in the production of tubing, particularly tubing of relatively small diameters and long length. Such machines typically bend the materials on a cylindrical mandrel which is supported within a loop or bight of a belt that must be moved relative to stationary support surfaces that generate friction and resistance to belts movement usually making it necessary to rotate the mandrel by power means. Also such machines attempt to keep the belt in contact with the maximum amount of the circumferential surface of the mandrel and the wood material deposited thereon but a gap is formed between the point at which the belt first contacts the mandrel and the point where the belt comes out of contact with the mandrel. In this gap, materials tend to come out of contact with the mandrel. When the materials are wood veneer, the leading edge of the veneer separates from the cylindrical surface so that when the leading edge of the veneer reenters the confines of the belt and mandrel, the veneer is usually shattered by the pressure applied by the belt. In machines where a continuous layer is wound on the mandrel the problem requires careful attention only at the beginning of the cycle of winding. The problem becomes particularly aggravated where tubes are to be made with separate, multiple layer and the leading edge of each layer must be carefully guided to reenter the feed gap between the belt and the mandrel.